AM79C930 datasheet(64/161 Pages) AMD

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P R E L I M I N A R Y

Am79C930

Am79C930 Device ISA Plug And Play Mode Memory And I/O Resource Requirements

Memory Range

Memory Size

I/O Range

I/O Size

MBA*+0000h –

32 Kbytes

IOBA**+0000h – IOBA**+000Fh

16 bytes

MBA*+7FFFh

and I/O 0279h and I/O 0A79h

0 bytes

and I/O 0203h – I/O 03FFh (one byte only)

*MBA = ISA Plug and Play Memory Base Address

**IOBA = ISA Plug and Play I/O Base Address

Note that since the Am79C930 device’s memory

mapped resources are all accessible through the Local

Memory

Address

and

I/O

Data

Ports

(SIR2,3,4,5,6,7), it is possible to program the ISA Plug

and Play Memory Base Address, and Memory upper

limit Address or range length for descriptor 0, such that

the Am79C930 device is assigned no memory space.

(This is accomplished by assigning all 0s for both the

Memory Base Address and the Memory range length

value. The ISA Plug and Play utility can be instructed to

make this selection through appropriate Resource Data

programming.) By assigning

no memory space to the

Am79C930 device, the Am79C930 device will become

an I/O only device. Such an arrangement may be con-

venient for systems in which there is not enough total

available memory space to allow the Am79C930 device

to use a full 32K block of memory. Note that when this

option is chosen, the total amount of bus bandwidth re-

quired to perform all of the necessary accesses to the

Am79C930-based system will be increased somewhat,

because of the indirect nature of the I/O method of ac-

cess to Am79C930-based resources.

The Am79C930 device requires the use of a single IRQ

channel. Any of the following channels within an

ISA Plug and Play system may be utilized by the

Am79C930 device:

IRQ 4, 5, 9, 10, 11 or 12.

ISA Plug and Play Memory Resources — While the

system memory space of the Am79C930 device only

accommodates access to 32 Kbytes of memory, the

Am79C930 device uses device select and bank select

bits in SIR1 in order to access a total of 256K of memory

space. Note that ISA accesses to memory locations

7C00h–7FFFh

(1K

total

space)

will

sometimes

correspond to the same physical locations as ISA ac-

cesses to Plug and Play resource data locations

0000h–03FFh, i.e., the correspondence will occur only

when the device and bank select bits of SIR1 are point-

ing at the upper page of the 128K Flash memory ad-

dress space. The following table indicates the mapping

of the 256 Kbytes of physical memory space into the

32 Kbytes of memory:

Am79C930 Device ISA Plug And Play Mode Memory Map

ISA Address in Memory

SIR1[5:3]

Size of Space

Physical Memory

MBA+0000h – MBA+7FFFh

000

32 Kbytes

SRAM Memory 0 0000h – 0 7FFFh

MBA+0000h – MBA+7FFFh

001

32 Kbytes

SRAM Memory 0 8000h – 0 FFFFh

MBA+0000h – MBA+7FFFh

010

32 Kbytes

SRAM Memory 1 0000h – 1 7FFFh

MBA+0000h – MBA+7FFFh

011

32 Kbytes

SRAM Memory 1 8000h – 1 FFFFh

MBA+0000h – MBA+7FFFh

100

32 Kbytes

Flash Memory 0 0000h – 0 7FFFh

MBA+0000h – MBA+7FFFh

101

32 Kbytes

Flash Memory 0 8000h – 0 FFFFh

MBA+0000h – MBA+7FFFh

110

32 Kbytes

Flash Memory 1 0000h – 1 7FFFh

MBA+0000h – MBA+7FFFh

111

32 Kbytes

Flash Memory 1 8000h – 1 FFFFh

TOTAL:

256 Kbytes

*MBA = ISA Plug and Play Memory Base Address

When

accessing

Am79C930

memory

resources

through ISA memory cycle accesses, the upper 9 bits of

the ISA memory address will be used to check for a

match of the address range assigned to the Am79C930

device by the Plug and Play configuration program (i.e.,

the Memory Base Address = MBA, and Memory range

length). The Plug and Play configuration program will

have written a memory base address value into the

Memory Base Address registers (Plug and Play ports

40h and 41h). The ISA Plug and Play memory base

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